I've read three books this month, all of them interesting. This one, however, is one of the most interesting, delightful books I've ever come across. I'd heard about it for years but had no idea what it was about, which made it perfect for my personal reading challenge: twelve books (at the least) about which I know little or nothing. After reading this, I can honestly tell you that no one can tell you what it's about. No one can prepare you for the joy of shifting and curving along the path Calvino mischievously, and expertly, guides you. It's usually listed as experimental fiction. It should be shelved under "required reading for people who truly love language and story for the sake of story".
This is a book meant to be savored. Don't pick it up expecting to read it in one sitting or even one weekend (though you may persevere better than I). Enjoy it. Chew it up slowly. Have fun. And definitely enjoy the ride.